OS X Virtual Machines

You are absolutely right, Apple very specifically does not want farms of terminal servers (they earn no money that way, they need to sell hardware) and their licensing does not allow that. You could look into a product like Aqua Connect but I know that path isn't cheap or easy, and it's not true virtualization with individual operating systems per user.

There's always the option of racking a bunch on Minis, I suppose!

Thanks for the info, @alexjdale . I hadn't heard of Aqua Connect. Have you used it before? I'm reading up on their website now.

There's a variety of ways to read the EULA, so definitely get your legal folks to make a ruling. There's three ways I've heard of it being read:

1. Two versions of OS X per instance of Apple hardware (so one Mac, two VMs running OS X)

2. Two versions of a specific version of OS X per instance of Apple hardware, but you can then stack them (so one Mac, two VMs running OS X 10.9.x, two VMs running 10.10.x, etc.)

3. Three versions of a specific version of OS X per instance of Apple hardware. This interpretation is based on the EULA referencing two "additional" OS X installs, which implies that the Apple hardware is running something other than OS X (like ESXi), there's one VM running OS X and that then two more OS X VMs. The two other OS X VMs are the "additional". (So one Mac running a baremetal virtualization solution, three VMs running OS X 10.9.x, three VMs running 10.10.x, etc.)

I am not a lawyer and will not advise if any of these are the correct interpretation of the EULA from Apple's point of view. Get actual lawyers to figure it out. :-)

Fortunately, the technical aspects are more straightforward. I gave a talk at this past year's JNUC where I discuss virtualizing OS X:

https://derflounder.wordpress.com/2014/11/04/bringing-the-casper-suite-to-life-with-virtual-test-environments-session-video-from-jnuc-2014-now-available/

I gave a similar talk at the Penn State MacAdmins Conference in June:

https://derflounder.wordpress.com/2015/08/12/session-videos-now-available-from-penn-state-macadmins-conference-2015/

https://derflounder.wordpress.com/2015/07/09/slides-from-the-virtualization-session-at-penn-state-macadmins-conference-2015/

I used it a bit back in the 10.6 days, so my experience with it is all but useless at this point. It might be worth a trial.

I also agree with the above recommendation to have your legal team read the EULA and make a judgment, because Apple will not help you sort this out (I've tried, with the response to make our own interpretation, Apple will not "bless" anything). Option 3 with a bare-metal hypervisor and three VMs per Mac would be the best you could do, that much is certain.

Also, you need to figure out how to have users remote into them (presumably from Windows systems), are you looking for an RDP solution or VNC?

The VM licensing issue is not the real problem for you. Its that Apple forbids you from using it as a terminal server. You really don't need a lawyer to interpret this section of the EULA:

H. Remote Desktop Connections. Subject to the terms and conditions of this License, when remotely connecting from another computer or electronic device (each a “Device”) to an Apple-branded computer that is running the Apple Software (for purposes of this Section, such Apple-branded computer is referred to as the “Home Mac”), whether through the Screen Sharing feature or through any other means: (i) only one (1) Device may remotely connect at any one time, whether directly or indirectly, to control the graphical desktop session of the Apple Software that is running and being displayed on the Home Mac; and (ii) a reasonable number of Devices may remotely connect at the same time for the sole purpose of simultaneously observing the same graphical desktop session of the Apple Software that is running and being displayed on the Home Mac, as long as they do not control the Apple Software in any way; but (iii) only one (1) Apple-branded Device may remotely connect at any one time, whether directly or indirectly, to control a separate graphical desktop session of the Apple Software that is different from the one running and being displayed on the Home Mac, and such connection may only be made through the Screen Sharing feature of the Apple Software.

I don't think it could be much clearer from the text in the EULA quoted above that the actual plan your boss wants to do is not legal. Though I am not a lawyer, I am going to trust that interpretation. ;)